1. Field of the Disclosure
The present disclosure relates to a power supply system for electric vehicle and control method thereof, and more particularly to a power supply system for electric vehicle configured to selectively charge a high voltage battery or a low voltage battery using an external AC power source, and a control method of a power supply system for electric vehicle.
2. Discussion of the Related Art
The information disclosed in this Discussion of the Related Art section is only for enhancement of understanding of the general background of the present disclosure and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
In recent years, with the aim for reducing CO2 discharge in an attempt to prevent global warming and air pollution, hybrid electric vehicles (HEVs) that are provided with a secondary battery and that use both an engine and a motor as a power source, have become increasingly popular, and electric vehicles (EVs) that are provided with a secondary battery and that emit no exhaust gas are also starting to attract attention, where an electric motor is driven by electricity to operate the EV, and the battery supplies electricity to the electric motor.
EVs generally refer to those which utilize electricity for power to a large extent, and typical EVs include an HEV (Hybrid Electric Vehicle), a PHEV (Plug-in Hybrid Electric Vehicle), and an EV (Electric Vehicle).
Generally, a power system of an EV includes a main battery (high voltage battery) supplying a driving power to a driving motor, a BMS (Battery Management System), a sub-battery (low voltage battery) providing a driving power to other vehicular electronic equipment and a host of electric devices.
An inverter may act as an intermediary between battery and electric motor. That is, an inverter converts a high DC (direct current) voltage generated by the main battery (high voltage battery) to an AC (alternating current) signal to control a motor. A low voltage DC-DC Converter (LDC) converts electric power of a high voltage battery into a direct current. That is, the LDC switches a direct current to an alternating current, boosts or drops the alternating current using coil, transformer, capacitance, etc., rectifies the resulting alternating current to a direct current and supplies electricity suitable for voltages used in respective electrical loads. In further details, the LDC converts the high voltage generated by the main battery (high voltage battery) to a low voltage, and outputs the low voltage to charge the sub-battery (low voltage battery).
Meanwhile, charging of a main battery may be implemented by connecting a charging plug installed at a battery charging station to an EV. In a case an AC power is supplied from outside by connection of the charging plug, an OBC (On-Board Charger) mounted inside the EV converts an AC power to a high DC voltage to charge the main battery.
The OBC is one of electrical equipment receiving a driving power from a sub-battery, such that if the sub-battery is discharged, the OBC may not be normally driven. As a result, if the sub-battery is discharged, the OBC cannot operate, such that even if an AC power is supplied through a charging plug, the main battery cannot be charged, whereby the EV cannot be supplied with a driving power to disadvantageously make the EV inoperable.
Another disadvantage is that the conventional OBC can charge only the main battery using an AC power and cannot charge the sub-battery, such that a user must inconveniently prepare a separate charging equipment to charge the sub-battery.